Various multi-panel glazing units are known. One such unit is composed of two pressed, hollow, glass bodies. The open faces of the two bodies are sealed together to form a unit for a glass wall. Another well-known example is the automotive windshield wherein two glass sheets are joined with an adhesive polymer interlayer. A further example is a double pane window wherein an intervening space is evacuated to prevent heat transfer.
The present invention is primarily concerned with a further type of multi-panel glazing unit. This unit is commonly referred to as a fire window. Such a glazing is mounted in a fire wall, or door. It is designed to provide transparency, while protecting against rapid spreading of flames in case of fire. Ordinary, single-pane glazing units tend to shatter in a fire, thus enabling flames to spread rapidly. Organic materials tend to be flammable, as well as creating noxious fumes.
It has been proposed to employ a construction similar to the multi-pane automotive safety glass. In this construction, the glass will still shatter, but the interlayer will tend to hold the broken glass in place. However, the interlayer is an organic material which will rapidly disintegrate itself.
Another proposed construction embodies spaced panes sealed together with a spacer. The intermediate space may be either evacuated, or filled with a liquid. This construction also fails to adequately fulfill the requirements of a fire window.
It is a purpose of the present invention to provide a multi-panel glazing unit with an enclosed material that produces an effective fire window. The enclosed material, to be effective, must meet these requirements:
1. It must be transparent.
2. It must be capable of producing a foam under thermal influence.
3. The foam produced must function as an insulator, that is, must resist the transfer of heat.
4. The material must adhere to the glass both prior to and after foaming.
5. The material should not shrink, crack, or discolor over a period of time.
Fire window materials, heretofore available, have satisfied one or more of these requirements, but not all. The insulating and glass adherence requirements have been especially difficult to meet. Prior structures, when exposed to flame, have tended to either fracture and disintegrate, or to rapidly transfer heat between panes.
The present invention provides a fluid sol for enclosure between spaced glass panes to produce a fire window. The fluid sol is transparent, ages well, and foams when exposed to heat. The foam produced adheres to the glass, acts as an insulator, resists deterioration, and is non-toxic.